Accessing modem via router?

So, basically, I have a Linksys modem (default firmware) connected to the WAN port of a WRT54GL running Tomato.

I can't, of course, access the modem's config pages, unless I plug an ethernet cable into the modem itself, or connect via WiFi (which I've switched off anyway, as I have no use for it - I just use the WRT54GL's WiFi).

So, basically, I have a Linksys modem (default firmware) connected to the WAN port of a WRT54GL running Tomato.

I can't, of course, access the modem's config pages, unless I plug an ethernet cable into the modem itself, or connect via WiFi (which I've switched off anyway, as I have no use for it - I just use the WRT54GL's WiFi).